VCPU over commit issue

Unable to over commit vcpu usage on Ocata version.Installed Openstack Ocata version with 6 hypervisor which consists of 72 vcpu.Default cpu over commit ratio is 16:1 and therefore i should get 72*16 vcpu,but unfortunately when vcpu usage goes beyond 76 ,multiple IP's getting assigned to newly created instance and not properly booting up.Is there any configuration change required to use over commit vcpu feature.

Comments

Thanks a lot for the response.Application user is calling api's and creating VM,so will try to incorporate this in it..Also if we create just one or two VM's also multiple IP's getting assinged after it cross the vcpu,its not getting over committing

I am not creating multiple instances at a time.Even if i create single instance after VCPU has gone beyond the limit ,it will assign multiple IP and VM installation fails..Any other way to prevent this ?

Once it is stuck it is hard to get it going again. I've had to 1) reboot the controller and 2) then on the compute nodes, restart nova-compute, neutron-linuxbridge-agent, and libvirtd 3) stay calm and carry on.

Ideally, I should try to figure out exactly where the problem is coming from.